'Behind the motor': Can electric vehicles sustain not drain the grid?

Some two million Australian households with rooftop solar panels have done much to transform their involvement in the electricity sector and what they park in their garages may one day be just as disruptive.

The first electric vehicles equipped to both charge from and discharge into the grid will soon be an option when the new Nissan Leaf goes on sale in Australia by mid next year.

Other models will likely follow with the same bi-directional charging capability, and with Bloomberg New Energy Finance tipping electric cars to be cheaper upfront than diesel or petrol ones by 2024, numbers of these mobile power plants could accelerate.

Going with the flow: Nissan's new Leaf comes with bi-directional charging capacity, making it potentially a mini, mobile power station.

Iain Macgill, director of the Centre for Energy & Environmental Markets at the University of NSW, said rapid improvements in battery technology meant "there's potentially a very substantial load in terms of energy and power" in the coming wave of electric cars.

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Just as these vehicles could provide a huge drain on the grid if owners plugged in to recharge at the same time, they may also supply a major new source of electricity to support the grid, especially during peaks.

In theory, if 10 per cent of Australia's 20 million vehicles were electric and they discharged into the grid at a rate 4 kilowatts, the resulting 8 gigawatts would be the equivalent of NSW's average load now, Professor Macgill said.

With typical households using about 20 kilowatt-hours a day of electricity, a fully charged Leaf with its 40 kilowatt-hour battery could run a household's appliances for two days, Professor Macgill said. Other vehicles coming, such as Hyundai's Kona with as much as 64 kW-hour in storage, could supply even longer if appropriately equipped.

Ali Asghar, a senior Bloomberg NEF associate, forecasts that by 2040 about 40 per cent of the vehicle market could be electric. That would imply a "behind the motor" capacity of 350 gigawatt-hours, equivalent to the size of the Snowy 2.0 pumped hydro scheme planned by the federal government.

Many regulatory and market hurdles will need to be cleared before vehicle-to-grid becomes significant, he said, adding that fleet applications may be the first to sign up.

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Carmakers such as Tesla set battery warranties on kilometres travelled and don't now support a discharge to the grid, Mr Asghar said: "It can have impacts on the degradation and life of the batteries."

"In the long term, it could be a marginal extra" for buyers considering an EV over an internal combustion engine-powered car, he said. "It makes the deal a little sweeter."

Wayne Harris, head of electrification and mobility at Nissan, said the company was confident the Leaf's bi-directional charging would not be detrimental to battery performance.

"The health of the batteries is paramount to every single thing we do," Mr Harris said.

"Essentially your car becomes a portable battery," he said. "It can play a role as one of those other items that you can control in your home and maximise efficiency ... in your power usage."

The Leaf, expected to retail at about $60,000, jointly shared Drive's Best Green Innovation award for 2018, with the unique charging "the key reason", said Stephen Ottley, head of testing at Drive.com.au.

Lance Douglas, director of business development at Charge Point, said his firm has prepared for the roll-out of bi-directional charging by EVs.

"Right now there's no trading framework" to take advantage of the dual charging, he said, adding that it was probably only a matter of time before one emerged.

"This is the most disruptive era for energy," Mr Douglas said. "It's also the the most disruptive era for vehicle makers."

The bi-directional charging capacity of the new Leaf has already drawn interest abroad, with a fleet of 1000 vehicles being tested in a vehicle-to-grid trial in the UK. Germany also last month granted the Japanese automaker first approval in Europe's biggest market for such cars to be an energy backstop.